Portable devices like mp3 players, game decks, laptops, notebooks, PDAs, cellular phones and the like usually comprise at least one output socket for connecting a headset. Digital cameras sometimes comprise a TV-out socket for putting out a video signal for display on a TV set. Future portable devices, particularly game decks like the Nokia® N-Gage, will be able to put out both audio and video signals. These game decks can then be used like non-portable video game consoles when being connected to a standard TV set and outputting the game graphics therewith. As the processing power of such portable devices, PDAs, smartphones and the like also more and more enables video playback functions it is desirable to output the video signal on a bigger screen than the internal one, to watch videos on a suitably big display.
Presently available are various plug types for audio or video signals, like the common 3.5 mm stereo plug, cinch type plugs, S-VHS plugs and many others. As the mere size of the plugs and particularly of their corresponding sockets in the electronic device has a great, if not decisive impact on the size of the electronic device, it is desirable to provide plug/socket connection systems being as small as possible. Also the number of plugs/sockets should correspondingly be kept as low as possible. The available size of a device will in the first place be used to place control elements, displays and the like. It is therefore undesirable to be forced to sacrifice a large part of the outer surface of a device to provide big and numerous connection sockets. Also it is desirable to have only a limited amount of standard plugs/sockets rather than the present vast variety of different, partially proprietary, connectors.
Thus a trend is to integrate as many functions as possible into one plug. There are two main drawbacks with this solution. On the one hand the resulting plugs will often not be compatible to standard plugs, i.e. be proprietary because of contacts being relocated compared to the standard arrangement, thus prohibiting a use with standard equipment and different devices. On the other hand a very strict integration, e.g. using only one ground connection for different signals (audio/video), and the fact that contacts/conductors will be located very close to one another, will lead to a decrease in signal quality and electrical problems (interferences, ground loops).
A solution being not satisfying for small electronic devices would be using two different dedicated connectors for audio and video, for example a combination of 3.5 mm stereo plug for audio and a 2.5 mm video plug for the video signals. The drawbacks of such a solution should be obvious.
While the 3.5 mm stereo audio plug has become a quasi standard for pure audio signals there is no comparatively small single plug available for both audio and video signals providing suitable shielding of the video signals; existing connectors like the SCART connector are not suitable for small electronic devices.
U.S. Pat. No. 6,069,960 describes as prior art a 3.5 mm audio plug wherein an additional contact is provided to transfer video signals. This video transmit plug is not compatible to conventional plugs, as the contact for the right stereo channel is displaced and instead the contact usually used for right audio is used for video signals. Further, as such a plug does not provide any shielding means the video signal is exposed to disturbances and video quality will be reduced, also because only a common audio and video ground is used. In this application a kind of active “plug-in” detection based on different impedances is described in order to detect the kind of the plug.
From the aforementioned it is apparent that there is a need for a compact single plug and socket for audio and video signals being small in footprint while also providing for a good electrical signal quality, and preferably being compatible to existing equipment and the standard 3.5 mm audio plug/socket, respectively. Therefore it is an object of the present invention to provide such a plug that is suitable for small portable electronic devices.